At first glance, Scott Rownin's Samsung Galaxy S III does not stand out. It receives and makes calls, chimes with incoming emails and text messages and displays a screen full of apps.

But when he gets behind the wheel and hits the road, the smartphone changes. A few seconds after he shifts the gear into drive, the phone falls silent and the apps on its home screen vanish, replaced by a shield with a winding road and the words "SafeRide." Tapping the screen or pressing the home button will not restore the device's normal settings. Its screen and hardware buttons will be disabled and audio muted as long as he is driving.

The lockdown of Rownin's phone is not a glitch; it is by design. His phone is temporarily disabled because it is using SafeRide, a new program the Westport resident has developed. It locks a phone automatically when a user is operating a vehicle with SafeRide hardware.

"It's like Nicorette for texting," Rownin said of SafeRide during a demo last week in downtown Westport. "The benefit there is that all of those little dings that make you want to grab your phone and see who just texted or emailed you go away. Eventually, you sort of kick the habit and move on."

SafeRide-equipped phones work normally when users are not driving and do not interfere with passengers' phones.

SafeRide is compatible with most mobile devices running Google's Android operating software. It consists of an approximately two-and-a-half-inch by one-inch device that plugs into a vehicle's cigarette-lighter console and an app on the driver's phone. The phone and the plugged-in device are linked by Bluetooth wireless-communication technology, which allows the phone to detect when the SafeRide beacon is within range.

He is targeting a July release for the Android version, with a suggested retail price of $49.95.

Rownin's product aims to combat an epidemic of distracted driving. At any time, about 660,000 drivers are talking on hand-held cellphones, equating to five percent of all American motorists during any "typical daylight moment," according to the National Highway Traffic Safety Administration. Forty-eight percent of drivers said they answer their cellphones while driving at least some of the time, and 58 percent continue to drive after answering the call, NHTSA also reports.

Transportation officials are especially concerned about texting while driving because it involves manual, visual and cognitive interaction, the three major forms of driver distraction.

Distracted driving is particularly pronounced among young drivers. Forty-nine percent of 21 to 24-year-olds and 44 percent of 18- to 20-year-olds said they have sent a text message or email while driving, according to a 2011 NHTSA survey.

"For teenagers especially, I think this is crucial," Rownin said. "The phone's in their hand, and they're always looking to see who texted them and who messaged them. This is a way to stop that behavior when they're driving."